Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

incident power
power in an electromagnetic wave that is traveling in an incident direction.
incoherent illumination
a type of illumination resulting from an infinitely large source of light that illuminates the mask with light from all possible directions. This is more correctly called spatially incoherent illumination.
induced voltage
voltage produced by a time-varying magnetic flux linkage.
See Faraday's law.
inductance
a parameter that describes the ability of a device to store magnetic flux. The units are henrys per meter.
induction furnace
a method of smelting or heating metals with eddy currents induced by a high-frequency coil surrounding the crucible.
induction generator
an induction machine operated as a generator. If the machine is connected to an AC system and is driven at greater than synchronous speed, the machine can convert mechanical energy to electrical form. The induction generator requires a source of reactive power.
induction machine
classification of any of a variety of electrical machines in which an AC current in the stator coils is used to produce a rotating magnetic flux that, by Faraday action, induces an AC voltage in a set of coils (the induction coils) on the machine's rotor. The rotor coils are shorted to cause a second AC current to flow in the rotor coils, which produces, in turn, a second rotating flux. The interaction of the rotor-and stator-produced fluxes creates torque.
induction motor

See induction machine
induction regulator

See induction voltage transformer
induction theorem
states that if the incident tangential magnetic and electric fields are known everywhere on some closed surface, then these fields may be replaced with equivalent electric and magnetic surface currents.
induction voltage transformer
specially constructed transformer with a rotating primary coil that is used to provide voltage regulation on individual power circuits. The secondary of an induction regulator is mounted on the stationary shell of cylindrical core, and the primary is mounted on a movable, center rotor. In the neutral position, the magnetic axes of the primary and secondary coils are oriented 90 degrees to each other, reducing the magnetic coupling to zero. In this position, energizing the primary does not induce voltage in the secondary; however, rotating the primary coil in either direction from the neutral position creates mutual flux linkage and causes a secondary voltage to appear.

Rotation in one direction causes secondary voltage to be in phase with the primary; rotation in the opposite direction causes secondary voltage to be out of phase with the primary. Voltage regulation is provided by connecting the primary coil across the line to be regulated and connecting the secondary coil in series with the load. By positioning the primary coil based on load demand in the line, secondary voltage can be used to adjust line voltage either up or down. Induction regulators are also equipped with a short-circuited coil mounted on the primary in spatial quadrature with the primary coil. In the neutral position, this coil has maximum coupling with the secondary coil, which minimizes the inductive reactance in the load line due to the secondary coil.
inductive coupling
a means of transferring electrical energy from one part (area) of a circuit to another part without requiring any ohmic (wire) connection. Instead, magnetic flux linkages couple two inductors (coils). The coils must be in close proximity in order to establish sufficient mutual inductance.
inductive discontinuity
a type of discontinuity that exhibits an inductive, or quasi-inductive, behavior. As an example, magnetic plane iris in metallic rectangular waveguides produces this type of response.
inductor
a two-terminal electrical element that satisfies a prescribed algebraic relationship in the flux-current (θ - I) plane.
inertia constant
the energy stored in an electric machine running at synchronous speed and given in megajoules per megavoltampere of machine rating.
infinite bus
an electrical supply with such large capacity that its voltage (and frequency, if AC) may be assumed constant, independent of load conditions. If a machine's capacity is small relative to the electric supply system to which it is connected, it may be assumed to be operating on an infinite bus.
input impedance
(1) when a voltage is applied to a conducting material, a current will flow through the material. The ratio of the voltage to the current is known as the input impedance and is a complex number with magnitude measured in units of ohms. See also Ohm's Law.

(2) impedance seen when looking into the input terminals of an antenna. input layer a layer of neurons in a network
that receives inputs from outside the network. In feedforward networks, the set of weights connected directly to the input neurons is often also referred to as the input layer.
inrush current
the transient current drawn by an electrical apparatus when it is suddenly connected to a power source. The inrush current may be larger in magnitude than the steady-state full-load current. The transient response is short in time and the electrical equipment generally supports the inrush current, provided it does not happen frequently. For a single transient, the thermal limit of the equipment is not reached, but if it is switched on and switched off several times within a short period, the temperature can rise very quickly. In case of transformers, the inrush current is not sinusoidal even if the voltage is due to the hysteresis of the ferromagnetic core.
insertion loss
(1) worst-case loss of the device across the stated frequency range. The loss due to the insertion of the unit in series with a signal path.

(2) transmission loss of an RF or microwave component or system, typically measured in decibels.
insolation
incident solar radiation.
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